US2622229A - Flash tube circuit - Google Patents

Description

Dec. 16, 1952 w, LORD 2,622,229

FLASH TUBE CIRCUIT Filed Dep. 21, 1950 5 i l k ME His Attorney.

Patented Dec. 16, 1952 FLASH TUBE CIRCUIT Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 21, 1950, Serial No. 201,900

Claims.

This invention relates to improved circuits for operating a plurality of flashtubes simultaneously, and has for an object the provision of an improved circuit in which the operation of one fiashtube initiates substantially simultaneous operation of one or more other flashtubes. Other objects and advantages will appear as the description proceeds.

It is known that flashes of brilliant light can be produced by suddenly discharging a capacitor through gas-filled or vapor-filled electric discharge devices, commonly called fiashtubes. Usually the flashtubes have a starting electrode, of a conventional type, and the capacitor is charged to a voltage which will discharge through the flashtube only when a discharge-initiating electric impulse is applied to the starting electrode of the fiashtube.

In using flashtubes with cameras for flash photography, it is often desirable to use a plurality of fiashtubes, operated simultaneously, to achieve the most pleasing lighting effects. Ordinary camera shutter contacts, of the type now furnished with cameras designed for flash photography, can carry sufficient electric current to provide the initiating impulse for a single flashtube. In accordance with the present invention, an improved circuit is provided in which the operation of a first flashtube, controlled by the camera shutter contacts, supplies the discharge-initiating impulse to operate one or more other fiashtubes simultaneously.

The features of this invention which are believed to be novel and patentable are pointed out in the claims which form a part of this specification. For a better understanding of the invention, reference is made in the following description to the accompanying drawing, in which the single figure is a circuit diagram of an improved fiashtube circuit embodying the present invention.

Referring now to the drawing, a capacitor I is charged by any suitable means, such as a conventional voltage-doubler rectifier circuit comprising rectifiers 2 and 3, capacitor 4, and transformer 5. The primary winding 5 of transformer 5 is energized in the customary manner from any suitable source of alternating current.

Connected in parallel across capacitor l are two .flashtubes 6 and 1. Each flashtube has two principal electrodes and a starting electrode, as is customary in such tubes. Flashtube 6 has an anode 8, a cathode 9 and a starting electrode llJ. Flashtube I has an anode H, a cathode I 2 and a starting electrode [3. Each of these flashtubes, and the components immediately associated therewith inclosed by broken lines l4 and i5 respectively, may be mounted as a separate unit for disposition at any desired location about the object to be photographed.

A transformer It has a primar winding I1 and a secondary winding I8. Secondary winding [8 is connected between anode 8 and starting electrode lil, as shown. A voltage divider comprising resistors l9 and in series is connected. between anode 8 and cathode 9, as shown. A.

capacitor 2! is connected in series with primarywinding ll between anode 3 and tap 22 of the voltage divider. A switch 23, which may be the conventional camera shutter contacts, is connected in parallel with resistor 20 as shown.

' When capacitor l is charged, there is a voltage drop across resistor 21] which charges capacitor 2 I. When the camera shutter is operated, switch 23 closes, and capacitor 2| discharges through primary Winding ll. This applies a dischargeinitiating impulse to starting electrode [0, which initiates discharge of capacitor 1 through flashtube 6.

Transformer 24 has a primary winding 25 and a secondary winding 26. Secondary winding 26 is connected between anode l l and starting electrode l3, as shown. An electric discharge device 21, which may be a thyratron, has an anode 28, a cathode 29 and a control electrode 30. Primary winding 25 is connected between anode H and anode 28. A capacitor 3| is connected between cathode 29 and an anode ll, so that winding 25. device 27 and capacitor 3i are connected in series.

A voltage divider comprising resistors 32, 33, 34, 35, 36 and 31 in series is connected across capacitor l as shown, so that progressively more negative voltages are provided at taps 38, 39, 49, 4| and 42. Cathode 29 is connected through resistor 43 to tap 40. Control electrode 30 is connected through resistor 44 to a more negative tap 4i. When three-position switch 45 is in position C, as shown in the drawing, control electrode 30 is also connected through a capacitor 46 to the still more negative tap 42. These connections normally apply a sufficient negative bias to electrode 30 to maintain device 21 nonconductive.

When capacitor begins to discharge through fiashtube 6 in response to closing of switch 23, the voltage across capacitor I begins to decrease suddenly, and the potential at tap 42 therefore becomes less negative. This applies a relatively positive impulse to control electrode 3i] through I3, which initiates current fiow through flashtube.

then continues to discharge The ac- I. Capacitor I through the two flashtubes in parallel.

tion occurs so rapidly, that for all practical purposes the flashtubes operate simultaneously.

If desired, other flashtubes can be connected in parallel with fiashtube I at terminals 41, 58 and 49. In this way, several flashtubes maycon: veniently be operated from conventional camera shutter contacts.

With switch d5 in position A, flashtube i can be operated independently, with an adjustable time delay, upon closing switch 50; Switch 5e-is connected through an adjustable resistor 5|, a fixed resistor 52, a capacitor 5-3-and-switch 45 to control electrode 3! The circuit junction 54 between resistor 52 and capacitor 53 is connected through resistor 55 to tap 38. A capacitor 56 is connected between circuitjunction 54 and anode II. When switch 50 is closed, capacitor 55 beins to discharge at a rate determined by the combined resistance of resistors SI and 52. As this capacitor discharges, control electrode 39 becomes more positive, and when the negative bias normally applied to this control electrode is overcome, device 21 suddenly becomes conductive to apply a discharge-initiating impulse to starting electrode I3. Since the rate of discharge of capacitor 56 can be adjusted by varying the value ofadjustableresistor 5I, a time delay of desired value can be obtained.

Withswitch 45 in position B, fiashtube 'i can beoperated by light striking a phototube 57. Tube-51 is'connected in series with resistor-58 between anode I I and tap 39. lhe circuit junction 59 between tube 51 and resistor 58 i connectedthrough a capacitor 6% and switch 45'to control electrode 30. Also, when switch 45 is in position B, a resistor BI is connected in-parallel with resistor 44. When light strikes phototube 51, a-positiveimpulse is applied to control electrodeSO, which-initiates operation of fiashtube I. In-this way, one or more flashtubes may be operated remotely by a flash of light from any other fiashtube.

A neon glow lamp 52 may be connected in parallel with resistor 32, as shown. This lamp is designed to light only when capacitor I is charged to about 90% of its maximum-voltage. Therefore, lamp 62 operates as an indicator to showthat capacitor I is charged and that the circuit is ready to operate. Upon-discharge of capacitor I, the flashtubes become de-ionized, since the voltage-doubler power supply does not provide sufficient current to maintain current flowthrough the flashtubes.

Having described the principle of this invention and the best mode in which I have contemplated applying that principle, I wish it to be understood that the apparatus described is illustrative only, and that other means can'beemployed without departing-from the true scope of theinvention.

What I claim as new and desire to secure by Letters Patent-of the United States is:

1.- A- flashtubecircuit comprising first and second flashtubes each having at least two principal electrodes and a starting electrode, a capacitor connected across said first flashtube, means for charging said capacitor, means to apply an electric impulse to the starting electrode of said first flashtube to initiate discharge of said capacitor therethrough, and means responsive to the resulting decrease in voltage. across said capacitor for applying an electric impulse to the starting electrode of said second flashtube.

2. A fiashtube circuit comprising first and second capacitors, means for charging said capacitors, first and second flashtubes connected in parallel across said first capacitor, each of said fiashtubes having at least two principal electrodes and a starting electrode and being of a type which at maximum capacitor voltage will conduct current only upon application of an electric impulse to its starting electrode, means to apply an electric impulse to the starting electrode of said first fiashtube to initiate discharge of said first capacitor therethrough, a transformer having 2, primary winding and a secondary winding, said sec ondary winding being connected between the starting electrode and one of the principal electrodes of said second fiashtube, an electric discharge device having at least two principal electrodes and a control electrode, said primary winding, said second capacitor and said discharge device being connected in series, means biasing said discharge device to be normally nonconductive, and means to apply an electric impulse to said control electrode responsive to a decrease in voltage across said first capacitor, thereby discharging said second capacitor through said discharge device and said primary winding, whereby a discharge-initiating electric impulse is applied to the starting electrode of said second fiash--- tube;

3. A flashtube circuit comprising a first capacitor, first and second flashtubes connecting in parallel across said first capacitor, each of said flashtubes having an anode, a cathode and a startingielectrode, means for charging said first capacitor to a potential such that the capacitor discharges suddenly through the flashtubes only upon application of electric impulses to the respective starting electrodes, thereby producing flashes of brilliant light, a first transformer having a primary winding and a secondary winding, the secondary winding of said first transformer being connected between the anode and the'starting electrode of said first fiashtube, a second capacitor connected inserie with the primary winding of said first transformer, means to charge said second capacitor, means'to discharge said second capacitor through the primary winding of said first transformer to apply a'discharge initiating electric impulse to the starting electrode of said first fiashtube, a voltage divider having a plurality of taps, said voltage divider being connected across said first capacitor, a second-transformer having a primary windingand a secondary-winding, the secondary winding-of said second transformer being connected between the anode andthestarting.electrode of saidsecc- 0nd fiashtub'e, an electric discharge device having an anode, a cathode and a control electrode, the. primary winding of said second transformer being: connected between the anode of said sec ond-flashtube and the anode of said electric dis-- charge device, a, third capacitor connected between the anode of said second fiashtube and the cathode of said electric discharge device,- theucathode of .said electric discharge. device being connected to a tap of said voltage divider, a resistor connected between said control electrode and a more negative tap of said voltage divider, whereby said electric discharge device is biased to be normally nonconductive, and a fourth capacitor connected between said control electrode and a still more negative tap of said voltage divider, whereby the decrease in voltage across said first capacitor upon initiationof its discharge through said first fiashtube applies a relatively positive impulse to said control electrode, thereby causing said third capacitor to discharge through said electric discharge device and the primary winding of said second transformer to apply a discharge-initiating impulse to the starting electrode of said second fiashtube. 4. A flashtube circuit including a first and at least a second fiashtube each having at least two principal electrodes and a starting electrode, a capacitor coupled across said first fiashtube, means for charging said capacitor, means to apply an electric impulse to the starting electrode of said first fiashtube to initiate discharge of said capacitor therethrough, a voltage dividing means coupled across said capacitor, and an electric discharge device having the input thereof coupled to said voltage dividing means and the output thereof coupled to the starting electrode of said second fiashtube, said device being responsive to the resulting decrease in voltage across said voltage dividing means due to discharge of said capacitor for applying an electric impulse to the starting electrode of said second fiashtube.

5. A fiashtube circuit including a first and at least a second fiashtube each having at least two principal electrodes and a starting electrode, a capacitor coupled across said first fiashtube, means for charging said capacitor, means to apply an electric impulse to the starting electrode of said first flashtube to initiate discharge of said capacitor therethrough, voltage dividing means coupled across said capacitor, selective switching means having a movable switch arm adapted to selectively engage any one of a plurality of fixed contacts, a first one of said fixed contacts being coupled to said voltage dividing means, a photo-tube circuit coupled to a second one of said fixed contacts, an adjustable time delay circuit coupled to a third one of said fixed contacts, and an electric discharge device having the input thereof coupled to the movable switch arm of said selective switching means and the output thereof coupled to the starting electrode of said second fiashtube.

HAROLD W. LORD.

REFERENCES CITED UNITED STATES PATENTS Name Date Lord May 23, 1950 Number

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